FR2613835A1 - Device for moving and rotating a tool inside a tube and its use for inspecting the tubes of a steam generator - Google Patents

Abstract

The device comprises a flexible pipe 22, in which is placed a flexible element 21 over the entire length of the pipe 22, including end parts outside the pipe 22. The tool 20 is fixed onto one of the end parts of the flexible element 21 and the other part interacts with a drive means 11 for rotating the flexible element 21 inside the pipe 22. The device also comprises a torsionless winder/unwinder 14 for storing the pipe 22, a puller/pusher 15 and a guide pipe 16 joining the puller/pusher to the entry of the tube 3 into which the tool 20 is introduced. The device can be used in particular for inspecting the tubes 3 of a steam generator of a pressurised water nuclear reactor, the tool 20 being an inspection and measurement probe.

Description

 The invention relates to a device for moving and rotating a tool inside a very long tube and its use for controlling the tubes of a heat exchanger. of an air cooler or of a steam generator, in particular, of a steam generator of a bare nuclear pressurized water reactor.

 The steam generators of key nuclear pressurized water reactors comprise a bundle consisting of a very large number of tubes of great length and of small diameter. These tubes have a diameter close to 0.02 m and a length of 1 order of 25 m. The tubes are bent into a U at their middle part and their ends are crimped into the tube plate of the steam generator. The beam is arranged vertically in the envelope of the steam generator. the straight parts of the tubes being held by horizontal spacer plates and the U-folded middle parts being juxtaposed at the upper part of the bundle to form a structure called a bun whose maintenance is ensured by anti-vibration V-shaped bars inserted between each row of tubes.

 The bundle of a steam generator of a nuclear reactor with an electrical power of 900 MW comprises more than three thousand tubes and the bundle of a steam generator of a nuclear reactor with an electrical power of 1,300 MW more of five thousand tubes.

 It is necessary. after mounting the steam generator and before putting it into service and also. after a certain period of operation of the nuclear reactor, carry out certain checks on the bundle tubes and on the holding devices for these tubes.

 It is necessary, for example, to check the distances between the tubes and the anti-vibration bars at the level of the bun, too much play that can lead to wear of the tubes at the anti-vibration bars, under the effect of thermohydraulic phenomena while 'too little play can lead to wear by area friction the ideal play is around 0.3 mm.

 It is also necessary to check the wall of the tube. in its crimped area inside the tube plate and in the vicinity of the outlet face of this tube plate. Indeed, the swaging operation which makes it possible to crimp the tube can increase the risk of cracking of this tube in its deformed part or in the transition zone between the deformed part and the non-deformed part of the tube. Generally, the expansion operation is supplemented by an expansion operation of the tube transition zone and it is necessary to control the state of deformation of the tube in the expansion zone and in the expansion zone.

 These controls. when they are made before the steam generator is put into service, make it possible to assess the risks of the appearance of faults in certain areas of the bundle or possibly to detect a manufacturing or assembly defect.

 In the steam generator in service, the bundle tubes are subjected to very significant stresses of mechanical, hydraulic and thermal origin. Certain parts of these tubes are very sensitive to corrosion and wear caused by the contacting of these tubes with the pressurized water constituting the primary fluid of the reactor and with the feed water of the steam generator.

 It is therefore necessary to regularly check the tubes of the steam generators after they have been put into service, during the periods of shutdown of the nuclear reactor which are used for the control and maintenance of the nuclear reactor.

 Control means have therefore been designed and produced comprising probes which can be moved inside the tubes of a steam generator. either before or after commissioning.

 The control probe must be inserted and moved between the tubes by means of guidance and displacement means, some of which must be placed in the water box of the steam generator, under the inlet face of the tube plate.

These displacement means are remotely controlled from a control station located near the steam generator.

 The control device includes means making it possible to know at any time the precise position of the probe inside the tube, in order to be able to locate the faults which can be detected.

 On the other hand, the realization of the means for moving the probe is complicated by the fact that this probe must pass through the tubes in curved zones situated at their upper part. The difficulties are increased when it comes to controlling the tubes located at the central part of the beam, the upper curved or arched part of which has a small radius of curvature.

 In addition, the detection and localization of certain types of defect can only be carried out or can be implemented efficiently by using a probe which is rotated inside the tube. around an axis substantially coincident with 1 axis of the tube.

 For example. checking the clearances between the tubes and the anti-vibration bars, checking the wear of the tubes at the anti-vibration bars, detecting cracks in the tubes, including in their bent parts and in particular at the outlet of the tube plate and checking for play and wear between the tubes. in the area of the small hangers, as well as the profile control of the swivel area and the transition area of the tubes or any other area can only be achieved by using a rotating probe or at least are much more efficient by using a rotating probe.

 These checks can be carried out both by eddy currents and by ultrasound.

 Control devices have been proposed comprising a motor ensuring the rotation of the probe and accompanying this probe in its movements inside the tube. It is then necessary to use an engine with a small diameter less than 2 cm. In addition, the measurement signals supplied by the probe must be transmitted to the outside of the steam generator by a measurement line connected to the probe via a very small rotating collector. The miniaturization of the auxiliary devices equipping the probe makes the tube inspection device fragile and makes maintenance operations of this device difficult, especially when the probe has been used in irradiated environment. The manufacture of this device turns out to be more delicate and expensive.

 In addition. the torque developed by the probe's rotation motor is generally low, so that the probe can lock in the event of significant friction such as that which is brought into play when the probe passes through the parts curves such as small hangers.

 The reliability of the control is therefore not satisfactory and it is not always possible to locate faults precisely. Generally, it is not even possible to check the small beam hangers, the length of the probe, its drive motor and the rotating collector being too great.

 There are also known devices for moving and rotating a tool in a tube such as a steam generator tube of a pressurized water nuclear reactor. In such devices. the transmission of the rotational movement to the tool can be ensured by a flexible element of elongated shape also ensuring the translational movement of the tool inside the tube. The tool is integral with one of the ends of the flexible element, the other end of which is engaged with motor means for its rotation and for its displacement in translation.

 However, such devices are limited as regards the translational movements in the tube at relatively short distances of the order of 0.5 m.

 The devices according to the prior art which ensure the displacement and the rotation of a probe or a tool inside a tube of great length and of small diameter, use a motor and a rotating collector accompanying the probe or tool in its movements inside the tube.

 The object of the invention is therefore to propose a device for moving and rotating a tool inside a very long tube.

the tool being fixed to the end of an elongated flexible element capable of transmitting a torque for the rotation of the tool and connected at its opposite end to motor means for rotation, this simple embodiment device having very safe operation that can be used to control the steam generator tubes of pressurized water nuclear reactors, in all areas of these tubes and in particular in the area of small hangers, without having to use resources for driving and controlling the position of the tool as well as the means of transmitting electrical signals, inside the tube to be machined or controlled.

 For this purpose, the device according to the invention further comprises - a flexible displacement and guide duct having an internal diameter greater than the diameter of the flexible element and an external diameter less than the internal diameter of the tube, the element flexible being placed inside the duct, over the entire length of this duct and having end parts connected to the tool and to the driving means, placed outside the duct.

- a winder and unwinder device for the storage of the conduit in which the flexible element is placed.

- And a push-pull device and guide means interposed between the storage device and one end of the tube. for the introduction and movement of the conduit, the flexible element and the tool inside the tube.

 The invention also relates to the use of the device for checking the tubes of a steam generator of a pressurized water nuclear reactor.

 We will now describe, by way of nonlimiting example, with reference to the appended figures, an embodiment of a device according to the invention and its use for checking the tubes of a steam generator. a pressurized water nuclear reactor.

 Figure 1 is a simplified elevational view of the entire device, during an operation of checking a tube of a steam generator.

 FIG. 2 is a section view on a large scale of a current part of the duct and of the hose of the device shown in FIG. 1.

 FIG. 3 shows a probe for monitoring the tubes of a steam generator, according to a first embodiment.

 FIG. 4 shows a probe for monitoring the tubes of a steam generator, according to a second embodiment.

 In Figure 1, there is shown schematically the water box 1 of a steam generator, hemispherical in shape and integral with the tube plate 2 of the steam generator. The tubular plate 2 is pierced with a large number of holes over its entire thickness making it possible to receive the ends of the tubes 3 constituting the bundle of the steam generator.

 In FIG. 1, only one tube 3 has been shown, in a completely conventional manner, the diameter of the tube having been considerably enlarged in relation to its length, to facilitate representation. In reality, this tube has a diameter of the order of 0.02 m and a length between its two ends 3a and 3b crimped in the tubular plate 2, of the order of 25 m.

 The middle part 3c of the tube 3 is folded to form a semi-circular hanger.

The hangers of all the tubes of the bundle constitute by their juxtaposition the upper part of generally hemispherical shape of the bundle called a bun.

 The straight parts of the tubes 3 are held inside the envelope of the steam generator by horizontal spacer plates such as 4.

 The hangers 3c of the tubes juxtaposed in the bun are held in place by anti-vibration bars 5 available in a V shape.

 The water box has two compartments la and lb separated by a partition 7. One of the compartments is placed in communication with a pipe of the primary circuit bringing the pressurized water at high temperature coming from the reactor vessel and the - be with a pipe allowing the return of cooled pressurized water in the steam generator to the nuclear reactor vessel. The compartments 1a and 1b of the water box 1 each have an inspection opening or manhole 8a, 8b, respectively, allowing the introduction of a tool into the water box and its positioning under the face d inlet 2a of the tubular plate 2, on which the ends 3a and 3b of the tubes 3 are flush.

 The device according to the invention comprises a set of means located at a fixed position outside the water box of the steam generator and close to it.

 These means are constituted by an encoder 10.

a drive motor 1 1 and a rotary manifold 12 placed in series one after the other, on a common support 13 as well as a winder-unwinder 14 practically without twisting and a puller-pusher 15 interposed between the support 13 and the opening 8a of the water box 1 of the steam generator. The motor could also be placed in a position offset laterally or in height relative to the flexible hose 21.

 The pusher-shooter 15 is extended by a flexible guide duct 16, the end of which is connected to a carrier 17 fixed under the tubular plate and making it possible to place the end of the duct 16 opposite to the pusher-shooter 15, coinciding with the 'one end of the tube 3.

 The carrier 17 is of a known type and includes means allowing it to be fixed inside tubes close to the tube 3 in which the control is carried out The carrier 17 is associated with a machine of a known type which is introduced into the water box of the steam generator and fixed under the tube plate and which allows the carrier 17 to be placed successively in coincidence with the ends of the tubes to be checked.

 The guide duct 16 is connected by one of its ends to the outlet of the pusher-puller 15 and at its other end to the carrier 17. This guide duct 16 is constituted by a stainless steel tube whose surface produced under the shape of a bellows has successive waves to give great flexibility to the duct.

 The tube control probe 20 which will be described in more detail with reference to FIGS. 3 and 4 is fixed to one end of an elongated flexible element 21, the other end of which is engaged with the motor. drive 1 1 for its rotation around its longitudinal axis.

 The flexible element 21 is arranged inside and over the entire length of a flexible conduit 22 constituted by a tubular sheath.

 In FIG. 2, it can be seen that the flexible element 21 has an outside diameter smaller than the inside diameter of the sheath 22, a radial clearance 23 being formed between these two elements.

 The flexible element 21 is constituted by a tubular steel cable frame 25 composed of wires wound in successive crossed layers.

The flexible sheath 22 is constituted by a simple tube made of a plastic material such as the
Rilsan.

 The outside diameter of the sheath 22 is slightly less than the inside diameter of the tubes 3 to be checked and the length of this sheath is of the order of 30 m.

 The length of the flexible element 21 is substantially equal to the length of the sheath 22 the end of this flexible element on which the probe 20 is fixed and 1 end in engagement with the drive motor 11, are however located at the outside of the sheath 22.

 The end of the sheath 22 adjacent to the drive means 11 of the flexible element 21 is fixed on the support 13 common to the encoder 10, to the motor 11 and to the manifold 12.

 The corresponding end of the hose 21 is connected in series to the manifold 12, to the motor 11 and to the encoder 10. This end can also be connected to the motor 11 in parallel with respect to the manifold and the encoder, in the case where the motor is placed in an offset position laterally or in height with respect to the flexible hose 21.

 The central channel "4 of the hose 21 allows the passage of the supply and measurement wires 26 of the probe 20.

 In FIG. 3, a probe 20 can be seen comprising a body 30 of profiled shape, one end 30a of which constitutes a connector allowing its junction at the end of the hose 21.

 Around the body 30 are arranged two sets of brushes 31 of annular shape for guiding and centering the probe 20 inside the tube 3 to be checked. The outside diameter of the brushes 31 is substantially equal to the inside diameter of the tubes 3.

 Between the two sets of annular brushes 31, the body 30 of the probe carries windings 32 for measurement by eddy currents. These measurement windings are connected to the electrical conductors 26 which allow the junction of the probe to the rotary collector 12, for its supply and the collection of the measurement signals.

 In FIG. 4, an alternative embodiment of the probe 20 can be seen. The probe shown has two successive parts 20a. 20b connected by a universal joint or a flexible sheath 34 or itself made up of two parts connected by a centering device 35.

 The end portion 20a of the probe is identical to the probe shown in Figure 3 which has just been described.

 Part 20b comprises a body 36 of profiled shape around which are arranged two sets of annular brushes 37 ensuring the guiding and centering of part 20b of the probe. Between the two sets of brushes 37, a circumferential coil 38 is wound, wound on the body of the probe and having as axis the longitudinal axis common to the two parts of the probe and to the junction sheath 34.

 The body 36 of the part 20b of the probe is connected by a flexible sheath 41 or a cardan joint to a junction piece 40 comprising a connector 40a allowing the assembly of the assembly of the probe 20 to the end of the hose 21 .

 The probe 20 constitutes, in the embodiment shown in FIG. 4, a flexible assembly of great length which can carry out several types of measurement at different locations in the tube.

 For the implementation of a control operation in a tube 3 of a steam generator, the device according to the invention is put in place as shown in FIG. 1.

 The flexible hose 21, disposed inside the flexible conduit 22, carries at one of its ends, outside the flexible conduit 22, a measurement probe 20, for example of the eddy current type.

 The other end of the flexible element 21.

also located outside the flexible conduit 22.

is mounted on the same axis as the encoder which makes it possible to determine at all times the orientation of the hose 21 and of the probe 20, during the rotation of the hose.

The structure of the flexible element 21 is in fact such that the rotational movements are transmitted to the probe with practically no torsion of the hose 21.

 Following the encoder 10, the hose 21 is engaged with the drive motor 11 which allows it to rotate at a regular and adjustable speed. from O to 30 rpm.

 The rotating collector allows the electrical supply of the probe and the collection of the measurement signals transmitted by the electrical conductors 26.

 The winder-unwinder storage device 14 in which the flexible conduit 22 can be stored, inside which the hose 21 is placed, is of the type described in French patent application 2,575,874. Such a device makes it possible to wind and unwinding of a flexible cable of which one end is fixed, practically without twisting of this cable or conduit.

 In the case of the device according to the present invention, the winder-unwinder 14 is capable of containing the whole of the conduit 22 inside which the flexible hose 21 is disposed, this conduit having a length of the order of 25 m.

 The puller-pusher 15 is a puller-pusher with motorized rollers of the conventional type.

 For the implementation of the device according to the invention for the control of a tube 3, the carrier 17 on which is fixed the end of the flexible conduit 16 is placed at the inlet of the tube 3, so as to put in coincidence the entry of the tube and the exit of the conduit 16.

 The conduit 22 in which the hose 21 is placed carrying the probe 20 at its end is introduced into the conduit 16 by means of the push-pull device 15 which then ensures its movement up to the entrance of the tube 3. It is then possible to carry out various checks inside the tube, in the zone of crossing of the tubular plate 2, at the level of each of the spacer plates 4 and in the zone of the hanger 3c, in particular, at the level of the anti-vibration bars 5.

 In particular, a profile check of the tube can be carried out in its part 3a or in its part 3b crimped inside the tubular plate 2 or in its part 3c. This control will be carried out by rotating the probe 20, by means of the flexible, thanks to the motor 11, while ensuring a displacement at constant speed of the flexible sheath 22 and of the flexible thanks to the puller-pusher. a helical scan of the entire interior surface of the tube on which eddy current measurements are made continuously.

it is also possible to detect cracks in the tubes in the vicinity of the outlet face of the tube plate, by currents of
Eddy or by ultrasonic measurement.

it is also possible to carry out simultaneous ultrasonic and current checks
Eddy of certain zones of the tubes, the control probe being put in rotation. This control can be carried out continuously over the entire length of the steam generator tubes.

 it is also possible, in the case where the tube has been previously repaired by sleeving, to check the condition of the welds of the sleeves, by ultrasound.

 Finally, it is possible to carry out various checks in the area of the hangers and in particular the control of the distances between the tubes and between the tubes and the anti-vibration bars, in the bun constituting the upper part of the bundle.

 The probe shown in FIG. 4 makes it possible on the one hand to determine the position of the anti-vibration bars 5 located in the bun of the bundle, by virtue of the circumferential winding 38 of the part 20b of the probe and, on the other hand, to measure the 7eu existing between the tube 3 and the anti-vibration bar 5 with the windings 32 of the part 20a of the probe whose position has been determined.

 To carry out this position marking and this measurement, the probe is first of all moved inside the tube 3 only by a translational movement, thanks to the push-pull device 15 acting on the flexible sheath 22.

 This first movement of the probe 20 makes it possible to determine, thanks to the winding 38 of the part 20b of the probe, the precise position of the anti-vibration bars 5, this position being determined relative to the entry face of the tube plate 2 .

 When the probe has reached the outlet of the hanger 3c, the translational movement is interrupted by stopping the push-pull device 15. The position of all the anti-vibration bars 5 is then determined.

 The movement of the push-puller is reversed and the probe 20 is rotated at a constant speed of 20 revolutions / sec, thanks to the motor 11. The operation of the push-puller is controlled so as to move the probe at a rapid linear speed between the anti-vibration bars 5, the position of which has been perfectly determined and at a slow speed of the order of 20 mm / sec at each of the anti-vibration bars 5. This gives, at these anti-vibration bars vibratory 5, a helical displacement of the probe with a pitch of 1 mm / turn. This helical movement at slow speed allows precise recording of the play between the anti-vibration bars 5 and the tube 3, thanks to the windings 32 of the part 20a of the probe.

 We see that the main advantages of the device according to the invention are to dissociate the elements on which one exerts thrust or traction forces for the displacement of the probe in translation and the elements on which one exerts a torque allowing the setting in rotation of the probe.

 The device according to the invention also makes it possible to store a large length of flexible sheath and flexible cable in a device preventing practically any twisting and any deterioration of these flexible elements and allowing a rotation of a central flexible inside the '' a very long coiled sheath.

 All of the motor means and position control means of the device remain outside the tube during the control. which allows to easily increase the performance of these drive means and of these position tracking means. compared to the solutions of the prior art where these devices had to be introduced into the tube with the probe.

 In particular, it is possible to very precisely identify the position in translation and in rotation of the probe.

 In addition, the probe can easily penetrate into all parts of the bundle tubes and in particular into the small hangers of the tubes located at the central part of this bundle.

 The invention is not limited to the embodiment which has been described.

 Thus, instead of a hollow flexible element such as the flexible element 21 which has been described, it is possible to use a solid hose which makes it possible to transmit a large torque of up to 4 Nm and to cause tool or control means connected at its end at a high speed of the order of 50 revolutions / sec. This solution could be adopted. in particular, when the hose is connected to a tool carrying out machining in a tube, this machining requiring significant torque and speed.

Instead of measurement windings with
Eddy the probe of the measurement and control device moved in the tubes could carry an ultrasonic probe,
Indeed, the device according to the invention can be used not only for the control of the tubes of a steam generator but also for the control of any tube of great length and of small diameter whose mechanical or metallurgical state must be controlled carefully or to carry out any machining inside a tube of great length and small diameter.

Claims (15)

 1.- Device for moving and rotating a tool (20) inside a tube (3) of great length. the tool being fixed to the end of a flexible element (21) of elongated shape capable of transmitting a torque for the rotation of the tool (20) and connected at its end opposite the tool to means motors (11) for rotating. characterized in that it further comprises - a flexible conduit (22) for movement and guide having an internal diameter greater than the diameter of the flexible element (21) and an external diameter less than the internal diameter of the tube (3) . the flexible element (21) being placed inside the duct (22) over its entire length and having end parts connected to the tool (20) and to the motor means (11), located outside of the conduit (22), - a winder and unwinder device (14) for storing the conduit (22) containing the flexible element (21), - and a puller-pusher device (15) and guide means (16) interposed between the storage device (14) and one end of the tube (3) for the introduction and movement of the conduit (22), the flexible element (21) and the tool (20) inside of the tube (3).  2. A displacement device according to claim 1, characterized in that the flexible element (21) is produced in the form of a tubular conduit whose internal bore (24) allows the passage of electrical conductors (26) connected to the tool (20).  3. A displacement device according to claim 2, characterized in that the flexible element (21) comprises a tubular frame of steel rod composed of son wound in successive crossed layers.  4. A movement device according to any one of claims 2 and 3, characterized in that it further comprises an encoder (10) for determining the rotational position of the hose (21) around its axis and a collector rotating (12) to provide the electrical connection between the conductors (26) and an electrical supply device and / or a signal collection device.  5. A displacement device according to claim 4, characterized in that the motor means (11), the encoder (10) and the rotary manifold (12) are fixed on a common fixed support (13) to which is connected one end of the flexible conduit (22).  6. A displacement device according to any one of claims 1 to 5, characterized in that the tool (20) is a measurement and / or control probe.  7. A movement device according to claim 6, characterized in that the probe carries eddy current measurement windings (32, 38) or an ultrasonic probe.  8. A displacement device according to claim 6, characterized in that the probe (20) is in two parts (20a, 20b) connected by a flexible element (34), one of the parts (20a) carrying a first type of measuring coils with Foucault and the other part, a second type of measurement windings.  9.- Use of a displacement device according to any one of claims 6 to 8 for the control of the tubes (3) of a va va generator of a pressurized water nuclear reactor, by displacement of the probe (20) inside each of the tubes to be controlled successively, the steam generator comprising a water box (1) having inspection openings (8a, 8b) and the tubes (3) having their ends flush with the face inlet of a tubular plate (2) accessible inside the water box (1), characterized in that the drive means (11), the winder-unwinder storage device (1lui and the puller- pusher (15) are arranged outside the water box (1) near the steam generator, the guide means (16) being constituted by a flexible duct connected, at one of its ends, to the output of the push-puller (15) and, at its other end, to a carrier device (17) of known type capable of being fixed on the face of th input (2a) of the tubular plate (2), so as to successively put the outlet of the flexible conduit (16) in coincidence with the ends of the tubes (3) to be checked.  10.- Use according to claim 9, for checking the profiles of the tubes by rotary probe inside and / or in the vicinity of the tube plate (2).  11. Use according to claim 9, for the control of a part of the tubes (3c) of curved shape called a hanger remote from the inlet face (2a) of the tubular plate (2).  12.- Use according to claim 11, in the case of a steam generator comprising hangers (3c) held relative to each other by anti-vibration bars (5), for the eddy current control of the position of the anti-vibration bars (5) relative to the tubes (3) and for the measurement of the clearances existing between the tubes (3) and the anti-vibration bars (5).  13.- Use according to claim 12, characterized in that the determination of the position of the anti-vibration bars (5) by currents of Eddy is carried out by moving the probe (20) only in translation in the hanger (3c) of the tube (3) and that the clearance measurement is carried out by putting the probe (20) in rotation inside the tube, by l 'intermediate the flexible (21) and the motor means (11).  14.- Use according to claim 9 for the control of the tubes (3) of a steam generator over their entire length.  15.- Use according to any one of claims 9 to 14, characterized in that the flexible conduit (22) has a length close to 25 m.